Quantitative MR measurements of regional and global left ventricular function and strain after intramyocardial transfer of VM202 into infarcted swine myocardium

Gene therapy for diabetic foot ulcers: Interim analysis of a randomised, placebo-controlled phase 3 study of VM202 (ENGENSIS), a plasmid DNA expressing two isoforms of human hepatocyte growth factor

To evaluate the status of a 7-month phase 3 study conducted to test the effect of intramuscular injections of VM202 (ENGENSIS), a plasmid DNA encoding human hepatocyte growth factor, into the calf muscles of chronic nonhealing diabetic foot ulcers with concomitant peripheral artery disease. The phase 3 study, originally aimed to recruit 300 subjects, was discontinued because of slow patient recruitment. An unprespecified interim analysis was performed for the 44 subjects enrolled to assess the status and determine the future direction. Statistical analyses were carried out for the Intent-to-Treat (ITT) population and separately for subjects with neuroischemic ulcers, using a t-test and Fisher's exact test. A logistic regression analysis was also conducted. VM202 was safe and potentially should have benefits. In the ITT population (N = 44), there was a positive trend toward closure in the VM202 group from 3 to 6 months but with no statistical significance. Levels of ulcer volume or area were found to be highly skewed between the placebo and VM202 groups. Forty subjects, excluding four outliers in both arms, showed significant wound-closing effects at month 6 (P = .0457). In 23 patients with neuroischemic ulcers, the percentage of subjects reaching complete ulcer closure was significantly higher in the VM202 group at months 3, 4, and 5 (P = .0391, .0391, and .0361). When two outliers were excluded, a significant difference was evident in months 3, 4, 5, and 6 (P = .03 for all points). A potentially clinically meaningful 0.15 increase in Ankle-Brachial Index was observed in the VM202 group at day 210 in the ITT population (P = .0776). Intramuscular injections of VM202 plasmid DNA to calf muscle may have promise in the treatment of chronic neuroischemic diabetic foot ulcers (DFUs). Given the safety profile and potential healing effects, continuing a larger DFU study is warranted with modifications of the current protocol and expansion of enrolling sites.

Stem cell therapy combined with controlled release of growth factors for the treatment of sphincter dysfunction

Sphincter dysfunction often occurs at the end of tubule organs such as the urethra, anus, or gastroesophageal sphincters. It is the primary consequence of neuromuscular impairment caused by trauma, inflammation, and aging. Despite intensive efforts to recover sphincter function, pharmacological treatments have not achieved significant improvement. Cell- or growth factor-based therapy is a promising approach for neuromuscular regeneration and the recovery of sphincter function. However, a decrease in cell retention and viability, or the short half-life and rapid degradation of growth factors after implantation, remain obstacles to the translation of these therapies to the clinic. Natural biomaterials provide unique tools for controlled growth factor delivery, which leads to better outcomes for sphincter function recovery in vivo when stem cells and growth factors are co-administrated, in comparison to the delivery of single therapies. In this review, we discuss the role of stem cells combined with the controlled release of growth factors, the methods used for delivery, their potential therapeutic role in neuromuscular repair, and the outcomes of preclinical studies using combination therapy, with the hope of providing new therapeutic strategies to treat incontinence or sphincter dysfunction of the urethra, anus, or gastroesophageal tissues, respectively.

Gene therapy for diabetic peripheral neuropathy: A randomized, placebo-controlled phase III study of VM202, a plasmid DNA encoding human hepatocyte growth factor

VM202 is a plasmid DNA encoding two isoforms of hepatocyte growth factor (HGF). A previous phase II study in subjects with painful diabetic peripheral neuropathy (DPN) showed significant reductions in pain. A phase III study was conducted to evaluate the safety and efficacy of VM202 in DPN. The trial was conducted in two parts, one for 9 months (DPN 3-1) with 500 subjects (VM202: 336 subjects; and placebo: 164) and a preplanned subset of 101 subjects (VM202: 65 subjects; and placebo: 36) with a noninterventional extension to 12 months (DPN 3-1b). VM202 or placebo was administered to calf muscles on days 0 and 14, and on days 90 and 104. The primary end point in DPN 3-1 was change from baseline in the mean 24-h Numerical Rating Scale (NRS) pain score. In DPN 3-1b, the primary end point was safety, whereas the secondary efficacy end point was change in the mean pain score. VM202 was well-tolerated in both studies without significant adverse events. VM202 failed to meet its efficacy end points in DPN 3-1. In DPN 3-1b, however, VM202 showed significant and clinically meaningful pain reduction versus placebo. Pain reduction in DPN 3-1b was even greater in subjects not receiving gabapentin or pregabalin, confirming an observation noted in the phase II study. In DPN 3-1b, symptomatic relief was maintained for 8 months after the last injection suggesting that VM202 treatment might change disease progression. Despite the perplexing discrepancy between the two studies, the safety and long-lasting pain-relieving effects of VM202 observed in DPN 3-1b warrant another rigorous phase III study. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Current therapies for painful diabetic peripheral neuropathy (DPN) are palliative and do not target the underlying mechanisms. Moreover, symptomatic relief is often limited with existing neuropathic pain drugs. Thus, there is a great medical need for safer and effective treatments for DPN. WHAT QUESTION DID THIS STUDY ADDRESS? Can nonviral gene delivery of hepatocyte growth factor reduce pain in patients with DPN and potentially modify progression of the disorder? WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? Nonviral gene therapy can be used safely and practically to treat DPN. HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? As the first gene medicine to enter advanced clinical trials for the treatment of DPN, this study provides the proof of concept of an entirely new potential approach to the disorder.

Critical limb ischemia: Current and novel therapeutic strategies

Critical limb ischemia (CLI) is the advanced stage of peripheral artery disease spectrum and is defined by limb pain or impending limb loss because of compromised blood flow to the affected extremity. Current conventional therapies for CLI include amputation, bypass surgery, endovascular therapy, and pharmacological approaches. Although these conventional therapeutic strategies still remain as the mainstay of treatments for CLI, novel and promising therapeutic approaches such as proangiogenic gene/protein therapies and stem cell-based therapies have emerged to overcome, at least partially, the limitations and disadvantages of current conventional therapeutic approaches. Such novel CLI treatment options may become even more effective when other complementary approaches such as utilizing proper bioscaffolds are used to increase the survival and engraftment of delivered genes and stem cells. Therefore, herein, we address the benefits and disadvantages of current therapeutic strategies for CLI treatment and summarize the novel and promising therapeutic approaches for CLI treatment. Our analyses also suggest that these novel CLI therapeutic strategies show considerable advantages to be used when current conventional methods have failed for CLI treatment.

Hepatocyte Growth Factor Regulates the miR-206-HDAC4 Cascade to Control Neurogenic Muscle Atrophy following Surgical Denervation in Mice

Hepatocyte growth factor (HGF) has been well characterized for its roles in the migration of muscle progenitors during embryogenesis and the differentiation of muscle stem cells, but its function in adult neurogenic muscle atrophic conditions is poorly understood. Here we investigated whether HGF/c-met signaling has any effects on muscle-atrophic conditions. It was found that HGF expression was upregulated in skeletal muscle tissue following surgical denervation and in hSOD1-G93A transgenic mice showing severe muscle loss. Pharmacological inhibition of the c-met receptor decreased the expression level of pri-miR-206, enhanced that of HDAC4 and atrogenes, and resulted in increased muscle atrophy. In C2C12 cells, HGF inhibited phosphorylation of Smad3 and relieved TGF-β-mediated suppression of miR-206 expression via JNK. When extra HGF was exogenously provided through intramuscular injection of plasmid DNA expressing HGF, the extent of muscle atrophy was reduced, and the levels of all affected biochemical markers were changed accordingly, including those of primary and mature miR-206, HDAC4, and various atrogenes. Taken together, our finding suggested that HGF might play an important role in regard to neurogenic muscle atrophy and that HGF might be used as a platform to develop therapeutic agents for neuromuscular disorders.

Hepatocyte Growth Factor (HGF) Promotes Peripheral Nerve Regeneration by Activating Repair Schwann Cells

During the peripheral nerve regeneration process, a variety of neurotrophic factors play roles in nerve repair by acting on neuronal or non-neuronal cells. In this report, we investigated the role(s) of hepatocyte growth factor (HGF) and its receptor, c-met, in peripheral nerve regeneration. When mice were subjected to sciatic nerve injury, the HGF protein level was highly increased at the injured and distal sites. The level of both total and phosphorylated c-met was also highly upregulated, but almost exclusively in Schwann cells (SCs) distal from the injury site. When mice were treated with a c-met inhibitor, PHA-665752, myelin thickness and axon regrowth were decreased indicating that re-myelination was hindered. HGF promoted the migration and proliferation of cultured SCs, and also induced the expression of various genes such as GDNF and LIF, presumably by activating ERK pathways. Furthermore, exogenous supply of HGF around the injury site, by intramuscular injection of a plasmid DNA expressing human HGF, enhanced the myelin thickness and axon diameter in injured nerves. Taken together, our results indicate that HGF and c-met play important roles in Schwann cell-mediated nerve repair, and also that HGF gene transfer may provide a useful tool for treating peripheral neuropathy.

Effective control of neuropathic pain by transient expression of hepatocyte growth factor in a mouse chronic constriction injury model

Hepatocyte growth factor (HGF) is a multifunctional protein that contains angiogenic and neurotrophic properties. In the current study, we investigated the analgesic effects of HGF by using a plasmid DNA that was designed to express 2 isoforms of human HGF—pCK-HGF-X7 (or VM202)—in a chronic constriction injury (CCI) –induced mouse neuropathic pain model. Intramuscular injection of pCK-HGF-X7 into proximal thigh muscle induced the expression of HGF in the muscle, sciatic nerve, and dorsal root ganglia (DRG). This gene transfer procedure significantly attenuated mechanical allodynia and thermal hyperalgesia after CCI. Injury-induced expression of activating transcription factor 3, calcium channel subunit α2δ1, and CSF1 in the ipsilateral DRG neurons was markedly down-regulated in the pCK-HGF-X7–treated group, which suggested that HGF might exert its analgesic effects by inhibiting pain-mediating genes in the sensory neurons. In addition, suppressed CSF1 expression in DRG neurons by pCK-HGF-X7 treatment was accompanied by a noticeable suppression of the nerve injury–induced glial cell activation in the spinal cord dorsal horn. Taken together, our data show that pCK-HGF-X7 attenuates nerve injury–induced neuropathic pain by inhibiting pain-related factors in DRG neurons and subsequent spinal cord glial activation, which suggests its therapeutic efficacy in the treatment of neuropathic pain.—Nho, B., Lee, J., Lee, J., Ko, K. R., Lee, S. J., Kim, S. Effective control of neuropathic pain by transient expression of hepatocyte growth factor in a mouse chronic constriction injury model.

Magnetic resonance imaging for characterizing myocardial diseases

The National Institute of Health defined cardiomyopathy as diseases of the heart muscle. These myocardial diseases have different etiology, structure and treatment. This review highlights the key imaging features of different myocardial diseases. It provides information on myocardial structure/orientation, perfusion, function and viability in diseases related to cardiomyopathy. The standard cardiac magnetic resonance imaging (MRI) sequences can reveal insight on left ventricular (LV) mass, volumes and regional contractile function in all types of cardiomyopathy diseases. Contrast enhanced MRI sequences allow visualization of different infarct patterns and sizes. Enhancement of myocardial inflammation and infarct (location, transmurality and pattern) on contrast enhanced MRI have been used to highlight the key differences in myocardial diseases, predict recovery of function and healing. The common feature in many forms of cardiomyopathy is the presence of diffuse-fibrosis. Currently, imaging sequences generating the most interest in cardiomyopathy include myocardial strain analysis, tissue mapping (T₁, T_2, T₂*) and extracellular volume (ECV) estimation techniques. MRI sequences have the potential to decode the etiology by showing various patterns of infarct and diffuse fibrosis in myocarditis, amyloidosis, sarcoidosis, hypertrophic cardiomyopathy due to aortic stenosis, restrictive cardiomyopathy, arrythmogenic right ventricular dysplasia and hypertension. Integrated PET/MRI system may add in the future more information for the diagnosis and progression of cardiomyopathy diseases. With the promise of high spatial/temporal resolution and 3D coverage, MRI will be an indispensible tool in diagnosis and monitoring the benefits of new therapies designed to treat myocardial diseases.

In vivo magnetic resonance elastography to estimate left ventricular stiffness in a myocardial infarction induced porcine model

PURPOSE

To estimate change in left ventricular (LV) end-systolic and end-diastolic myocardial stiffness (MS) in pigs induced with myocardial infarction (MI) with disease progression using cardiac magnetic resonance elastography (MRE) and to compare it against ex vivo mechanical testing, LV circumferential strain, and magnetic resonance imaging (MRI) relaxometry parameters (T₁ , T₂ , and extracellular volume fraction [ECV]).

MATERIALS AND METHODS

MRI (1.5T) was performed on seven pigs, before surgery (Bx), and 10 (D10), and 21 (D21) days after creating MI. Cardiac MRE-derived MS was measured in infarcted region (MIR) and remote region (RR), and validated against mechanical testing-derived MS obtained postsacrifice on D21. Circumferential strain and MRI relaxometry parameters (T₂ , T₁ , and ECV) were also obtained. Multiparametric analysis was performed to determine correlation between cardiac MRE-derived MS and 1) strain, 2) relaxometry parameters, and 3) mechanical testing.

RESULTS

Mean diastolic (D10: 5.09 ± 0.6 kPa; D21: 5.45 ± 0.7 kPa) and systolic (D10: 5.72 ± 0.8 kPa; D21: 6.34 ± 1.0 kPa) MS in MIR were significantly higher (P < 0.01) compared to mean diastolic (D10: 3.97 ± 0.4 kPa; D21: 4.12 ± 0.2 kPa) and systolic (D10: 5.08 ± 0.6 kPa; and D21: 5.16 ± 0.6 kPa) MS in RR. The increase in cardiac MRE-derived MS at D21 (MIR) was consistent and correlated strongly with mechanical testing-derived MS (r(diastolic) = 0.86; r(systolic) = 0.89). Diastolic MS in MIR demonstrated a negative correlation with strain (r = 0.58). Additionally, cardiac MRE-derived MS demonstrated good correlations with post-contrast T₁ (r(diastolic) = -0.549; r(systolic) = -0.741) and ECV (r(diastolic) = 0.548; r(systolic) = 0.703), and no correlation with T₂ .

CONCLUSION

As MI progressed, cardiac MRE-derived MS increased in MIR compared to RR, which significantly correlated with mechanical testing-derived MS, T₁ and ECV.

LEVEL OF EVIDENCE

1 J. Magn. Reson. Imaging 2017;45:1024-1033.

Cardiac MR imaging: current status and future direction

Coronary artery disease is currently a worldwide epidemic with increasing impact on healthcare systems. Magnetic resonance imaging (MRI) sequences give complementary information on LV function, regional perfusion, angiogenesis, myocardial viability and orientations of myocytes. T2-weighted short-tau inversion recovery (T2-STIR), fat suppression and black blood sequences have been frequently used for detecting edematous area at risk (AAR) of infarction. T2 mapping, however, indicated that the edematous reaction in acute myocardial infarct (AMI) is not stable and warranted the use of edematous area in evaluating therapies. On the other hand, cine MRI demonstrated reproducible data on LV function in healthy volunteers and LV remodeling in patients. Noninvasive first pass perfusion, using exogenous tracer (gadolinium-based contrast media) and arterial spin labeling MRI, using endogenous tracer (water), are sensitive and useful techniques for evaluating myocardial perfusion and angiogenesis. Recently, new strategies have been developed to quantify myocardial viability using T1-mapping and equilibrium contrast enhanced MR techniques because existing delayed contrast enhancement MRI (DE-MRI) sequences are limited in detecting patchy microinfarct and diffuse fibrosis. These new techniques were successfully used for characterizing diffuse myocardial fibrosis associated with myocarditis, amyloidosis, sarcoidosis heart failure, aortic hypertrophic cardiomyopathy, congenital heart disease, restrictive cardiomyopathy, arrhythmogenic right ventricular dysplasia and hypertension). Diffusion MRI provides information regarding microscopic tissue structure, while diffusion tensor imaging (DTI) helps to characterize the myocardium and monitor the process of LV remodeling after AMI. Novel trends in hybrid imaging, such as cardiac positron emission tomography (PET)/MRI and optical imaging/MRI, are recently under intensive investigation. With the promise of higher spatial-temporal resolution and 3D coverage in the near future, cardiac MRI will be an indispensible tool in the diagnosis of cardiac diseases, coronary intervention and myocardial therapeutic delivery.

Assessment of Regional Myocardial Work in Rats

Background—

Left ventricular (LV) motion and deformation is dependent on mechanical load and do therefore not reflect myocardial energy consumption directly. Regional myocardial work, however, constitutes a more complete assessment of myocardial function.

Methods and Results—

Strain was measured using high-resolution phase-contrast MRI in 9 adult male rats with myocardial infarction (MI) and in 5 sham-operated control animals. Timing of LV valvular events and LV dimensions were evaluated by cine MRI. A separate cohort of 14 animals (MI/sham=9/5) underwent measurement of LV pressure concurrent with identification of valvular events by Doppler-echocardiography for the purpose of generating a standard LV pressure curve, normalized to valvular events. The infarctions were localized to the anterolateral LV wall. Combining strain with timing of valvular events and a measurement of peak arterial pressure, regional myocardial work could be calculated by applying the standard LV pressure curves. Cardiac output and stroke work was preserved in the MI hearts, suggesting a compensatory redistribution of myocardial work from the infarcted region to the viable tissue. In the septum, regional work was indeed increased in MI rats compared with sham (median work per unit long-axis length in a mid-ventricular slice: 241.2 [224.1–271.2] versus 137.2 [127.0–143.8] mJ/m; P <0.001). Myocardial work in infarcted regions was zero. Additionally, eccentric work was increased in the MI hearts.

Conclusions—

Phase-contrast MRI, in combination with measurement of peak arterial pressure and MRI-derived timing of valvular events, represent a noninvasive approach for estimation of regional myocardial work in rodents.

The (PrS/HGF-pDNA) multilayer films for gene-eluting stent coating: Gene-protecting, anticoagulation, antibacterial properties, and in vivo antirestenosis evaluation

Vascular gene-eluting stents (GES) is a promising strategy for treatment of cardiovascular disease. Very recently, we have proved that the (protamine sulfate/plasmid DNA encoding hepatocyte growth factor) (PrS/HGF-pDNA) multilayer can serve as a powerful tool for enhancing competitiveness of endothelial cell over smooth muscle cell, which opens perspectives for the regulation of intercellular competitiveness in the field of interventional therapy. However, before the gene multilayer films could be used in vascular stents for real clinical application, the preservation of gene bioactivity during the industrial sterilization and the hemocompatibility of film should be taken into account. Actually, both are long been ignored issues in the field of gene coating for GES. In this study, we demonstrate that the (PrS/HGF-pDNA) multilayer film exhibits the good gene-protecting abilities, which is confirmed by using the industrial sterilizations (gamma irradiation and ethylene oxide) and a routine storage condition (dry state at 4°C for 30 days). Furthermore, hemocompatible measurements (such as platelet adhesion and whole blood coagulation) and antibacterial assays (bacteria adhesion and growth inhibition) indicate the good anticoagulation and antibacterial properties of the (PrS/HGF-pDNA) multilayer film. The in vivo preliminary data of angiography and histological analysis suggest that the (PrS/HGF-pDNA) multilayer coated stent can reduce the in-stent restenosis. This work reveals that the (PrS/HGF-pDNA) multilayer film could be a promising candidate as coating for GES, which is of great potential in future clinic application.

Multiscale Characterization of Impact of Infarct Size on Myocardial Remodeling in an Ovine Infarct Model

The surviving myocardium initially compensates the loss of injured myocardium after myocardial infarction (MI) and gradually becomes progressively dysfunctional. There have been limited studies on the effect of infarct size on temporal and spatial alterations in the myocardium during progressive myocardial remodeling. MI with three infarct sizes, i.e. 15, 25 and 35% of the left ventricular (LV) wall, was created in an ovine infarction model. The progressive LV remodeling over a 12-week period was studied. Echocardiography, sonomicrometry, and histological and molecular analyses were carried out to evaluate cardiac function, regional tissue contractile function, structural remodeling and cardiomyocyte hypertrophy, and calcium handling proteins. Twelve weeks after MI, the 15, 25 and 35% MI groups had normalized LV end diastole volumes of 1.4 ± 0.2, 1.7 ± 0.3 and 2.0 ± 0.4 ml/kg, normalized end systole volumes of 1.0 ± 0.1, 1.0 ± 0.2 and 1.3 ± 0.3 ml/kg and LV ejection fractions of 43 ± 3, 42 ± 6 and 34 ± 4%, respectively. They all differed from the sham group (p < 0.05). All the three MI groups exhibited larger wall areal expansion (remodeling strain), larger cardiomyocyte size and altered expression of calcium handing proteins in the adjacent myocardium compared to the remote counterpart from the infarct. A significant correlation was found between cardiomyocyte size and remodeling strain in the adjacent zone. A comparative analysis among the three MI groups showed that a larger infarct size (35 vs. 15% MI) was associated with larger remodeling strain, more serious impairment in the cellular structure and composition, and regional contractile function at regional tissue level and LV function at organ level.

Magnetic resonance imaging characterization of circumferential and longitudinal strain under various coronary interventions in swine

AIM: To compare the acute changes in circumferential and longitudinal strain after exposing a coronary artery to various interventions in swine.

METHODS: Percutaneous balloon angioplasty catheter was guided to location aid device (LAD) under X-ray fluoroscopy to create different patterns of ischemic insults. Pigs (n = 32) were equally divided into 4 groups: controls, 90 min LAD occlusion/reperfusion, LAD microembolization, and combined LAD occlusion/microembolization/reperfusion. Three days after interventions, cine, tagged and viability magnetic resonance imaging (MRI) were acquired to measure and compare left and right circumferential strain, longitudinal strain and myocardial viability, respectively. Measurements were obtained using HARP and semi-automated threshold method and statistically analyzed using unpaired t-test. Myocardial and vascular damage was characterized microscopically.

RESULTS: Coronary microemboli caused greater impairment in l left ventricular (LV) circumferential strain and dyssynchrony than LAD occlusion/reperfusion despite the significant difference in the extent of myocardial damage. Microemboli also caused significant decrease in peak systolic strain rate of remote myocardium and LV dyssynchrony. Cine MRI demonstrated the interaction between LV and right ventricular (RV) at 3 d after interventions. Compensatory increase in RV free wall longitudinal strain was seen in response to all interventions. Viability MRI, histochemical staining and microscopy revealed different patterns of myocardial damage and microvascular obstruction.

CONCLUSION: Cine MRI revealed subtle changes in LV strain caused by various ischemic insults. It also demonstrated the interaction between the right and left ventricles after coronary interventions. Coronary microemboli with and without acute myocardial infarction (AMI) cause complex myocardial injury and ventricular dysfunction that is not replicated in solely AMI.

Phase 1/2 open-label dose-escalation study of plasmid DNA expressing two isoforms of hepatocyte growth factor in patients with painful diabetic peripheral neuropathy

This study aimed to evaluate the safety and preliminary efficacy of intramuscular injections of plasmid DNA (VM202) expressing two isoforms of hepatocyte growth factor (HGF) in subjects with painful diabetic peripheral neuropathy (PDPN). Twelve patients in three cohorts (4, 8, and 16 mg) received two sets of VM202 injections separated by two weeks. Safety and tolerability were evaluated and the visual analog scale (VAS), the short form McGill questionnaire (SF-MPQ), and the brief pain inventory for patients with diabetic peripheral neuropathy (BPI-DPN) measured pain level throughout 12 months after treatment. No serious adverse events (AEs) were observed. The mean VAS was reduced from baseline by 47.2% (P = 0.002) at 6 months and by 44.1% (P = 0.005) at 12 months after treatment. The VAS scores for the 4, 8, and 16 mg dose cohorts at 6 months follow-up decreased in a dose-responsive manner, by 21% (P = 0.971), 53% (P = 0.014), and 62% (P = 0.001), respectively. The results with the BPI-DPN and SF-MPQ showed patterns similar to the VAS scores. In conclusion, VM202 treatment appeared to be safe, well tolerated, and sufficient to provide long term symptomatic relief and improvement in the quality of life in patients with PDPN.

Intramyocardial transfer of hepatocyte growth factor as an adjunct to CABG: phase I clinical study

The purpose of this phase I clinical trial was to evaluate the safety, tolerability and potential efficacy of VM202, naked DNA expressing two isoforms of hepatocyte growth factor, as an adjunct therapy to coronary artery bypass grafting (CABG) in patients with ischemic heart disease (IHD). Nine patients were assigned to receive increasing doses (0.5 to 2.0 mg) of VM202 injected into the right coronary artery (RCA) territory following completion of CABG for the left coronary artery territory. Patients were evaluated for safety and tolerability, and changes in myocardial functions were monitored via echocardiography, cardiac magnetic resonance imaging and myocardial single photon emission computed tomography throughout 6-month follow-up period. No serious complication related to VM202 was observed throughout the 6-month follow-up period. Global myocardial functions (wall motion score index, P=0.0084; stress perfusion, P=0.0002) improved during the follow-up period. In the RCA region, there was an increase in the stress perfusion (baseline vs 3-month, P=0.024; baseline vs 6-month, P=0.024) and also in the wall thickness of the diastolic and systolic phases. Intramyocardial injection of VM202 can be safely used in IHD patients with the tolerable dose of 2.0 mg. In addition, VM202 might appear to have improved regional myocardial perfusion and wall thickness in the injected region.

MDCT has the potential to predict percutaneous coronary intervention outcome in swine model: microscopic validation

BACKGROUND

Volumes and sizes of dislodged coronary microemboli vary during PCI so their effects at the left ventricular (LV) and cellular levels cannot be quantified. Furthermore, biopsy for tissue characterization is not an option in PCI patients.

PURPOSE

To characterize and validate microinfarct size, LAD territory where microinfarct were found using multidetector computed tomography (MDCT), histochemical staining and microscopy as a function of microemboli volumes and to scale the effects of microemboli volumes on LV function.

MATERIAL AND METHODS

Under X-ray guidance, a 3F catheter was inserted into LAD coronary artery of 14 pigs for delivering 16 mm(3) or 32 mm(3) of 40-120 μm microemboli. MDCT imaging/histochemical staining/microscopy were performed 3 days later and used to characterize regional and global structural and functional changes in LV by threshold/planimetric methods.

RESULTS

MDCT and ex-vivo methods were able to quantify microinfarct size and LAD territory where microinfarct was found as a function of volumes. However, MDCT and histochemical staining significantly underestimated microinfarct size and territory where microinfarct was found compared with microscopy. MDCT demonstrated the functional changes and showed a moderate correlation between LV ejection fraction and microinfarct size (r = 0.53). Microscopy provided higher spatial resolution for measuring islands of necrotic cells, which explains the difference in measuring structural changes.

CONCLUSION

MDCT showed the difference in microinfarct size and LAD territory as a function of microemboli volumes and scaled the changes in LV function. This experimental study gives clinicians a reference for the effects of defined microemboli volumes on myocardial viability and LV function and the under-estimation of microinfarct on MDCT.

SDF-1 in myocardial repair

Stem cell therapy for the prevention and treatment of cardiac dysfunction holds significant promise for patients with ischemic heart disease. Excitingly early clinical studies have demonstrated safety and some clinical feasibility, while at the same time studies in the laboratory have investigated mechanisms of action and strategies to optimize the effects of regenerative cardiac therapies. One of the key pathways that has been demonstrated critical in stem cell-based cardiac repair is (stromal cell-derived factor-1) SDF-1:CXCR4. SDF-1:CXCR4 has been shown to affect stem cell homing, cardiac myocyte survival and ventricular remodeling in animal studies of acute myocardial infarction and chronic heart failure. Recently released clinical data suggest that SDF-1 alone is sufficient to induce cardiac repair. Most importantly, studies like those on the SDF-1:CXCR4 axis have suggested mechanisms critical for cardiac regenerative therapies that if clinical investigators continue to ignore will result in poorly designed studies that will continue to yield negative results.

Insights into gene therapy for critical limb ischemia: the devil is in the details

Patients with critical limb ischemia (CLI) without potential for revascularization are currently without alternate therapies. Several gene therapy trials have tested angiogenesis factors, hepatic growth factor, vascular endothelial growth factor, and basic fibroblast growth factor, in rescuing CLI patients from amputation and mortality, and for improved quality of life including decreased pain, improved healing, and blood flow. Trial results have been variable, with HGF gene therapy being the most successful. New studies examining each of these angiogenic factors provide insights that will be useful for the design of effective therapeutic strategies.

Cardiac gene therapy in large animals: bridge from bench to bedside

Several clinical trials are evaluating gene transfer as a therapeutic approach to treat cardiac diseases. Although it has just started on the path to clinical application, recent advances in gene delivery technologies with increasing knowledge of underlying mechanisms raise great expectations for the cardiac gene therapy. Although in vivo experiments using small animals provide the therapeutic potential of gene transfer, there exist many fundamental differences between the small animal and the human hearts. Before applying the therapy to clinical patients, large animal studies are a prerequisite to validate the efficacy in an animal model more relevant to the human heart. Several key factors including vector type, injected dose, delivery method and targeted cardiac disease are all important factors that determine the therapeutic efficacy. Selecting the most optimal combination of these factors is essential for successful gene therapy. In addition to the efficacy, safety profiles need to be addressed as well. In this regard, large animal studies are best suited for comprehensive evaluation at the preclinical stages of therapeutic development to ensure safe and effective gene transfer. As the cardiac gene therapy expands its potential, large animal studies will become more important to bridge the bench side knowledge to the clinical arena.

MR fluoroscopy in vascular and cardiac interventions (review)

Vascular and cardiac disease remains a leading cause of morbidity and mortality in developed and emerging countries. Vascular and cardiac interventions require extensive fluoroscopic guidance to navigate endovascular catheters. X-ray fluoroscopy is considered the current modality for real time imaging. It provides excellent spatial and temporal resolution, but is limited by exposure of patients and staff to ionizing radiation, poor soft tissue characterization and lack of quantitative physiologic information. MR fluoroscopy has been introduced with substantial progress during the last decade. Clinical and experimental studies performed under MR fluoroscopy have indicated the suitability of this modality for: delivery of ASD closure, aortic valves, and endovascular stents (aortic, carotid, iliac, renal arteries, inferior vena cava). It aids in performing ablation, creation of hepatic shunts and local delivery of therapies. Development of more MR compatible equipment and devices will widen the applications of MR-guided procedures. At post-intervention, MR imaging aids in assessing the efficacy of therapies, success of interventions. It also provides information on vascular flow and cardiac morphology, function, perfusion and viability. MR fluoroscopy has the potential to form the basis for minimally invasive image-guided surgeries that offer improved patient management and cost effectiveness.

Human hepatocyte growth factor (VM202) gene therapy via transendocardial injection in a pig model of chronic myocardial ischemia

BACKGROUND

Hepatocyte growth factor (HGF) may stimulate angiogenesis. We examined the safety and therapeutic potential of the HGF plasmid (VM202) in pigs with chronic myocardial ischemia.

METHODS AND RESULTS

We delivered VM202 or vehicle transendocardially to 4 groups of pigs: vehicle control (n = 9); high-dose VM202 (n = 9); low-dose VM202 (n = 3); and normal control (no ischemia; n = 1). Pigs were killed 3, 30, and 60 days after injection. No adverse events were associated with VM202 treatment or delivery. Quantitative polymerase chain reaction indicated that heart injection sites had the highest levels of VM202 (day 3), which became almost undetectable by 30-60 days. Most nontarget tissues showed clearance of VM202 plasmid by day 30. Control and VM202-treated pigs did not differ in global functional data. Dobutamine-stressed myocardial-contrast echocardiogram suggested that VM202 may help preserve microvascular perfusion at 30 days; reperfusion velocity in ischemic myocardium decreased significantly in control (baseline to follow-up, 5.1 ± 1.9 to 2.7 ± 1.0; P = .031) but not in VM202 groups (high-dose: 3.1 ± 1.1 vs 3.1 ± 1.5 [P = .511]; low-dose: 3.8 ± 1.1 vs 3.9 ± 1.5 [P = .559]). Linear local shortening increased significantly from day 0 to 30 in VM202-treated versus control pigs (5.0 ± 4.7% vs 9.2 ± 7.5% vs 0.9 ± 5.8% [high-dose, low-dose, control, respectively]; P = .021).

CONCLUSIONS

Transendocardial delivery of VM202 was safe and may help to preserve microcirculatory perfusion and improve wall motion.

Coronary microembolization causes long-term detrimental effects on regional left ventricular function

OBJECTIVES

To investigate whether coronary microemboli have long-term effects on left ventricular (LV) function in an experimental model. Furthermore, to determine if first-pass perfusion and late gadolinium enhancement (LGE) patterns differs between small- and large-sized microemboli.

DESIGN

Six pigs underwent left anterior descending (LAD)-coronary microembolization with small-sized (40-120 μm, n ∼ 250 000) microemboli using a combined x-ray and MRI-system. MR-images before, one hour after and 7-8 weeks after microembolization were obtained. Results were compared to MRI obtained by large-sized (100-300 μm, n ∼ 7200) microemboli.

RESULTS

Cine MRI showed an acute drop in ejection fraction (from 49.5 ± 2.6% to 32.5 ± 2.8) that substantially recovered at 7-8 weeks (47.5 ± 3.2%). Regional LV-function assessed as circumferential, longitudinal and radial strain declined in both microinfarcts and remote regions followed by partial recovery at 7-8 weeks. The decline in LV function and the severe perfusion deficit from the small microemboli was similar to the large microemboli at one hour. There was a significant recovery in perfusion at 7-8 weeks in the microinfarcts. LGE demonstrated the microinfarcts at 7-8 weeks but not at one hour and the microinfarcts were confirmed by histopathology.

CONCLUSION

Microembolization causes long-term, regional LV dysfunction and this study confirmed the need of a comprehensive MRI-protocol for the detection of microinfarcts. These findings suggest that even small microemboli (40-120 μm in diameter), which may escape the distal protective devices influence cardiac function.

Quantitative and qualitative characterization of the acute changes in myocardial structure and function after distal coronary microembolization using MDCT

RATIONALE AND OBJECTIVES

To determine the potential of multidetector computed tomography (MDCT) in assessing, at 72 hours, the effects of distal coronary microembolization on myocardial structure and function.

MATERIALS AND METHODS

Microembolic material (total volume=16 mm(3) of 40-120 μm diameter) was selectively delivered in the left anterior descending coronary artery under x-ray fluoroscopy (n = 6 pigs). After 72 hours, 64-slice MDCT was used to assess LV function, perfusion, and viability. For comparison between the measurements at 80 kV, 120 kV, and postmortem we used Bland-Altman and Pearson correlation. Histochemical and histopathological staining was used for quantitative and qualitative characterization of microinfarct.

RESULTS

Cine MDCT showed the deleterious effects of microembolization on systolic wall thickening, LV volumes, and ejection fraction. Perfusion parameters, such as max upslope, peak attenuation, and time to peak, differed between microinfarct territory and remote myocardium. Inconsistency in visualizing microinfarct was observed using tube voltages of 80 kV and 120 kV. The extent of heterogeneous microinfarct was 4.5 ± 1.0 % of LV mass at 80 kV, 6.1 ± 0.9% LV at 120 kV, and 5.9 ± 1.1% LV on postmortem. There was significant difference in the extent of microinfarct measured on 80 kV MDCT compared with 120 kV and postmortem. Microscopic examination revealed the random distribution of obstructed microvessels surrounded by myocardial necrosis and inflammatory cells in all animals.

CONCLUSION

Both visible and nonvisible microinfarct cause perfusion deficit and LV dysfunction. MDCT is sensitive for quantifying early functional changes in LV caused by microembolization. Further improvement in spatial resolution of this technology is needed to improve visualization of microinfarct.

Incorporation of a left ventricle finite element model defining infarction into the XCAT imaging phantom

The 4D extended cardiac-torso (XCAT) phantom was developed to provide a realistic and flexible model of the human anatomy and cardiac and respiratory motions for use in medical imaging research. A prior limitation to the phantom was that it did not accurately simulate altered functions of the heart that result from cardiac pathologies such as coronary artery disease (CAD). We overcame this limitation in a previous study by combining the phantom with a finite-element (FE) mechanical model of the left ventricle (LV) capable of more realistically simulating regional defects caused by ischemia. In the present work, we extend this model giving it the ability to accurately simulate motion abnormalities caused by myocardial infarction (MI), a far more complex situation in terms of altered mechanics compared with the modeling of acute ischemia. The FE model geometry is based on high resolution CT images of a normal male subject. An anterior region was defined as infarcted and the material properties and fiber distribution were altered, according to the bio-physiological properties of two types of infarction, i.e., fibrous and remodeled infarction (30% thinner wall than fibrous case). Compared with the original, surface-based 4D beating heart model of the XCAT, where regional abnormalities are modeled by simply scaling down the motion in those regions, the FE model was found to provide a more accurate representation of the abnormal motion of the LV due to the effects of fibrous infarction as well as depicting the motion of remodeled infarction. In particular, the FE models allow for the accurate depiction of dyskinetic motion. The average circumferential strain results were found to be consistent with measured dyskinetic experimental results. Combined with the 4D XCAT phantom, the FE model can be used to produce realistic multimodality sets of imaging data from a variety of patients in which the normal or abnormal cardiac function is accurately represented.

Safety of a non-viral plasmid-encoding dual isoforms of hepatocyte growth factor in critical limb ischemia patients: a phase I study

We aimed to evaluate in a phase I dose-escalation study, the safety of intramuscular injections of a novel non-viral plasmid DNA expressing two isoforms of human hepatocyte growth factor (HGF) (VM202) in patients with critical limb ischemia (CLI). In total, 12 patients with CLI and unsuitable for revascularization were consecutively assigned to increasing doses (2 to 16 mg) of VM202 administered into the ischemic calf muscle at days 1 and 15. Patients were evaluated for safety and tolerability, changes in ankle- and toe brachial index (ABI and TBI), and pain severity score using a visual analog scale (VAS) throughout a 12-month follow-up period. Median age was 72 years and 53% of the patients were male. VM202 was safe and well tolerated with no death during the 12-month follow-up. Median ABI and TBI significantly increased from 0.35 to 0.52 (P=0.005) and from 0.15 to 0.24 (P=0.01) at 12 months follow-up. Median VAS decreased from 57.5 to 16.0 mm at 6 months follow-up (P=0.03). In this first human clinical trial, VM202, which expresses two isoforms of human HGF, appear to be safe and well tolerated with encouraging clinical results and thus supports the performance of a phase II randomized controlled trial.

Cardiovascular magnetic resonance imaging in delivering and evaluating the efficacy of hepatocyte growth factor gene in chronic infarct scar

BACKGROUND

In an open-chest model of acute infarct, epicardial delivery of hepatocyte growth factor (pCK-HGF-X7) gene improved left ventricle (LV) function. This study was designed to test (a) the efficacy of HGF gene in infarct scar delivered under magnetic resonance (MR) guidance and (b) the potential of multiple MR sequences in assessing the effects of pCK-HGF-X7 (treatment) and pCK-LacZ (control) genes on myocardial structure and function.

MATERIALS AND METHODS

Swine (six per group) were subjected to myocardial infarct, under X-ray fluoroscopy, and developed LV remodeling at 5 weeks. Multiple clinical magnetic resonance (MR) imaging sequences were performed before delivery of gene (at 5 weeks after infarction) and 5 weeks after delivery of gene. Under MR guidance, the active endovascular catheter was introduced into LV to transendocardially deliver 3.96 × 10(11) viral copies of pCK-HGF-X7 or pCK-LacZ in the border and core of the infarct scar. Histological evaluation of the infarct scar was performed 5 weeks after delivery of gene.

RESULTS

At 5 weeks after infarction, there was no significant difference in measured cardiovascular MR parameters between the groups. The pCK-HGF-X7 gene caused significant improvement in the following parameters (P<.05 for these parameters): three-dimensional (3D) strain (radial, circumferential, and longitudinal) and perfusion (maximum upslope, peak signal intensity, and time to peak) compared with control pCK-LacZ at 5 weeks after delivery of the genes. The ejection fraction was higher in pCK-HGF-X7-treated (43 ± 1%) than in pCK-LacZ control (37 ± 1%, P<.05) animals. These changes are associated with a decrease in infarct scar size (11.3 ± 2.0% in pCK-LacZ control and 6.7 ± 1.3% in pCK-HGF-X7-treated animals, P<.01) and infarct transmurality in four out of five infarct scar segments (P<.05) on delayed contrast-enhanced MR imaging. Microscopic study confirmed the increase in capillary (P<.05) and arteriole (P<.05) density of infarct scar in pCK-HGF-X7-treated animals compared with pCK-LacZ control animals.

CONCLUSIONS

Hepatocyte growth factor gene (pCK-HGF-X7) delivered under MR guidance into infarct scar ameliorated global function and 3D strain, increased regional perfusion and infarct resorption, and enhanced angiogenesis/arteriogenesis. This feasibility study provides novel approach and analysis methods and instrumentation for delivering and evaluating new locally delivered therapies.

Naked DNA expressing two isoforms of hepatocyte growth factor induces collateral artery augmentation in a rabbit model of limb ischemia

Hepatocyte growth factor (HGF) has been shown to induce angiogenesis in vivo and has potential as a candidate gene for 'therapeutic angiogenesis'. In vivo, two isoforms of HGF, HGF₇₂₃ and HGF₇₂₈, consisting of 723 and 728 amino acids, are generated through alternative splicing between exons 4 and 5, but the biological effects of their coexpression have not yet been elucidated. In this study, we generated a series of genomic-complementary DNA (cDNA) hybrids of the HGF gene by inserting various truncated intron 4 into the junction of exons 4 and 5 of HGF cDNA and analyzed the biological activities of these hybrid constructs. We showed that: (1) the hybrid called HGF-X7, which contained 1502 base pairs of intron 4, could drive a higher level of HGF expression than other hybrid constructs and cDNAs of each isoform alone; (2) the pCK vector was most efficient for the gene expression of HGF-X7; (3) coexpression of both isoforms of HGF could more efficiently induce the migration of human umbilical vein endothelial cell (HUVEC) and of the mouse myoblast cell line C₂C₁₂ myoblasts than a single isoform of HGF and human vascular endothelial growth factor (VEGF)₁₆₅ at a given concentration; (4) intramuscular administration of pCK-HGF-X7 resulted in transient and localized HGF expression in the injected muscle without an increase in the HGF protein levels in other tissues including serum; and (5) intramuscular injection of pCK-HGF-X7 could more efficiently increase the number of angiographically recognizable collateral vessels, as well as improve an intra-arterial Doppler wire-measured blood flow in the rabbit model of hindlimb ischemia when compared with the identical vector encoding VEGF₁₆₅ gene. These results showed that transfer of the genomic-cDNA hybrid of the HGF gene could be used as a potential therapeutic approach to human vascular diseases.

Heterogeneous microinfarcts caused by coronary microemboli: evaluation with multidetector CT and MR imaging in a swine model

PURPOSE

To directly compare the sensitivity of 64-section multidetector computed tomography (CT) with that of 1.5-T magnetic resonance (MR) imaging in the depiction and measurement of heterogeneous 7-8-week-old microinfarcts and the quantification of regional left ventricular (LV) function and perfusion in the territory of coronary intervention in a swine model.

MATERIALS AND METHODS

Approval was obtained from the institutional animal committee. An x-ray/MR system was used to catheterize the left anterior descending (LAD) coronary artery with x-ray guidance and to delineate the perfusion territory. The vessel was selectively microembolized in six pigs with small-diameter embolic material (40-120 microm, 250000 count). At 7-8 weeks after microembolization, multidetector CT and MR imaging were used to assess LV function, first-pass perfusion, and delayed contrast enhancement in remote myocardium and microinfarct scars. Histochemical staining with triphenyltetrazolium chloride (TTC) was used to confirm and quantify heterogeneous microinfarct scars. The two-tailed Wilcoxon signed rank test was used to detect differences between modalities and myocardial regions.

RESULTS

The LAD territory was 32.4% +/- 3.8(stadard error of the mean) of the LV mass. Multidetector CT and MR imaging have similar sensitivity in the detection of regional and global LV dysfunction and extent of microinfarct. The mean LV end-diastolic volume, end-systolic volume, and ejection fraction were 93 mL +/- 8, 46 mL +/- 4, and 50% +/- 3, respectively, on multidetector CT images and 92 mL +/- 8, 48 mL +/- 5, and 48% +/- 3, respectively, on MR images (P > or = .05). The extent of heterogeneous microinfarct was not significantly different between multidetector CT (6.3% +/- 0.8 of the LV mass), MR imaging (6.6% +/- 0.5 of the LV mass), and TTC staining (7.0% +/- 0.6 of the LV mass). First-pass multidetector CT and MR imaging demonstrated significant regional differences (P < .05) in time to peak between the heterogeneous microinfarct and remote myocardium (17.0 seconds +/- 0.3 and 12.4 seconds +/- 0.6, respectively, for multidetector CT and 17.2 seconds +/- 0.8 and 12.5 seconds +/- 1.0, respectively, for MR imaging).

CONCLUSION

Modern multidetector CT and MR imaging are sensitive modalities with which to depict heterogeneous microinfarcts and determine regional LV dysfunction and decreased perfusion in the territory of intervention. (c) RSNA, 2010.

Agreement of left ventricular mass in steady state free precession and delayed enhancement MR images: implications for quantification of fibrosis in congenital and ischemic heart disease

Background

Left ventricular mass (LVM) is used when expressing infarct or fibrosis as a percentage of the left ventricle (LV). Quantification of LVM is interchangeably carried out in cine steady state free precession (SSFP) and delayed enhancement (DE) magnetic resonance imaging (MRI). However, these techniques may yield different LVM. Therefore, the aim of the study was to compare LVM determined by SSFP and DE MRI in patients and determine the agreement with these sequences with ex vivo data in an experimental animal model.

Methods

Ethics committees approved human and animal studies. Informed written consent was obtained from all patients. SSFP and DE images were acquired in 60 patients (20 with infarction, 20 without infarction and 20 pediatric patients). Ex vivo MRI was used as reference method for LVM in 19 pigs and compared to in vivo SSFP and DE.

Results

LVM was greater in SSFP than in DE (p < 0.001) with a bias of 5.0 ± 6.7% in humans (r² = 0.98), and a bias of 7.3 ± 6.7% (p < 0.001) in pigs (r² = 0.83). Bias for SSFP and DE images compared to ex vivo LVM was -0.2 ± 9.0% and -7.7 ± 8.5% respectively.

Conclusions

LVM was higher when measured with SSFP compared to DE. Thus, the percentage infarction of the LV will differ if SSFP or DE is used to determine LVM. There was no significant difference between SSFP and ex vivo LVM suggesting that SSFP is more accurate for LVM quantification. To avoid intrinsic error due to the differences between the sequences, we suggest using DE when expressing infarct as a percentage of LVM.

Design and validation of Segment--freely available software for cardiovascular image analysis

Background

Commercially available software for cardiovascular image analysis often has limited functionality and frequently lacks the careful validation that is required for clinical studies. We have already implemented a cardiovascular image analysis software package and released it as freeware for the research community. However, it was distributed as a stand-alone application and other researchers could not extend it by writing their own custom image analysis algorithms. We believe that the work required to make a clinically applicable prototype can be reduced by making the software extensible, so that researchers can develop their own modules or improvements. Such an initiative might then serve as a bridge between image analysis research and cardiovascular research. The aim of this article is therefore to present the design and validation of a cardiovascular image analysis software package (Segment) and to announce its release in a source code format.

Results

Segment can be used for image analysis in magnetic resonance imaging (MRI), computed tomography (CT), single photon emission computed tomography (SPECT) and positron emission tomography (PET). Some of its main features include loading of DICOM images from all major scanner vendors, simultaneous display of multiple image stacks and plane intersections, automated segmentation of the left ventricle, quantification of MRI flow, tools for manual and general object segmentation, quantitative regional wall motion analysis, myocardial viability analysis and image fusion tools. Here we present an overview of the validation results and validation procedures for the functionality of the software. We describe a technique to ensure continued accuracy and validity of the software by implementing and using a test script that tests the functionality of the software and validates the output. The software has been made freely available for research purposes in a source code format on the project home page http://segment.heiberg.se.

Conclusions

Segment is a well-validated comprehensive software package for cardiovascular image analysis. It is freely available for research purposes provided that relevant original research publications related to the software are cited.

Persistent decline in longitudinal and radial strain after coronary microembolization detected on velocity encoded phase contrast magnetic resonance imaging

PURPOSE

To use velocity-encoded phase contrast (PC) MRI in assessing the effect of coronary microembolization on longitudinal and radial myocardial strain.

MATERIALS AND METHODS

A combined X-ray and MR system (XMR) was used for selective left anterior descending artery catheterization and microinfarct assessment in swine (n = 6). The embolized area at risk was defined on perfusion MRI followed by administration of a 7500 count (size = 100-300 microm) of the embolic agent. Quantification of strain and microinfarction was performed at 1 h and 1 week using PC-MRI and delayed enhancement (DE) MRI, respectively. At postmortem, sliced hearts were stained to define microinfarction.

RESULTS

Baseline longitudinal and radial strain did not differ between area-at-risk and remote myocardium. The embolized territory (area at risk) showed significant decline in longitudinal strain from -11.5 +/- 3.2% to 1.8 +/- 2.5% at 1 h (P < 0.05) and -3.9 +/- 1.1% at 1 week (P < 0.05). Similarly, regional radial strain progressively declined from 23.6 +/- 2.5% at baseline to 12.5 +/- 3.7% at 1 h (P < 0.05) and 4.8 +/- 5.0% at 1 week (P < 0.01). The size of microinfarction was not significantly different between DE-MRI and histochemical staining.

CONCLUSION

PC-MRI is sensitive in assessing changes in regional longitudinal and radial strain after coronary embolization. Longitudinal and radial strain of the hyperenhanced patchy microinfarction demonstrates persistent decline over the course of 1 week.

Allogeneic mesenchymal stem cells restore cardiac function in chronic ischemic cardiomyopathy via trilineage differentiating capacity

The mechanism(s) underlying cardiac reparative effects of bone marrow-derived mesenchymal stem cells (MSC) remain highly controversial. Here we tested the hypothesis that MSCs regenerate chronically infarcted myocardium through mechanisms comprising long-term engraftment and trilineage differentiation. Twelve weeks after myocardial infarction, female swine received catheter-based transendocardial injections of either placebo (n = 4) or male allogeneic MSCs (200 million; n = 6). Animals underwent serial cardiac magnetic resonance imaging, and in vivo cell fate was determined by co-localization of Y-chromosome (Y(pos)) cells with markers of cardiac, vascular muscle, and endothelial lineages. MSCs engrafted in infarct and border zones and differentiated into cardiomyocytes as ascertained by co-localization with GATA-4, Nkx2.5, and alpha-sarcomeric actin. In addition, Y(pos) MSCs exhibited vascular smooth muscle and endothelial cell differentiation, contributing to large and small vessel formation. Infarct size was reduced from 19.3 +/- 1.7% to 13.9 +/- 2.0% (P < 0.001), and ejection fraction (EF) increased from 35.0 +/- 1.7% to 41.3 +/- 2.7% (P < 0.05) in MSC but not placebo pigs over 12 weeks. This was accompanied by increases in regional contractility and myocardial blood flow (MBF), particularly in the infarct border zone. Importantly, MSC engraftment correlated with functional recovery in contractility (R = 0.85, P < 0.05) and MBF (R = 0.76, P < 0.01). Together these findings demonstrate long-term MSC survival, engraftment, and trilineage differentiation following transplantation into chronically scarred myocardium. MSCs are an adult stem cell with the capacity for cardiomyogenesis and vasculogenesis which contribute, at least in part, to their ability to repair chronically scarred myocardium.

Percutaneous transendocardial VEGF gene therapy: MRI guided delivery and characterization of 3D myocardial strain

BACKGROUND

Patients with myocardial infarcts have unfavorable left ventricular (LV) remodeling and devastating outcomes. This study was performed to determine whether VEGF-gene delivered transendocardially under MR-guidance improves LV three-dimensional (3D) strain (circumferential, longitudinal and radial), reduces infarct transmurality and increases vascular density in a canine model of permanent LAD coronary artery occlusion.

METHODS

Imaging was performed using a 1.5-T MR scanner. Three days after occlusion, a percutaneous catheter was advanced under MR-guidance into the LV chamber for transendocardial delivery of VEGF-gene therapy (n=6) or LacZ-gene as control (n=6) into infarcted and peri-infarcted myocardium. MRI was performed before (3 days) and after (50 days) the delivery of therapy using cine, tagged and delayed contrast enhancement. Histochemical and pathological stains were used to assess myocardial viability and vascular density, respectively.

RESULTS

Transendocardial delivery of VEGF-gene therapy and LacZ-gene under MRI guidance was successful in all animals. Significant improvement in 3D strain was observed within 50 days in treated animals. On the other hand, control animals demonstrated deterioration in regional strain over time. Significant reductions in infarct transmurality and increases in capillary and arteriole densities were also observed in VEGF-treated as compared to control animals.

CONCLUSION

MR-guided transendocardial delivery of VEGF-gene improved myocardial strain and enhanced transmural infarct resorption. This minimally invasive technique may be useful for delivery of local therapies, designed to promote angiogenesis or myogenesis.

Intracoronary injection of contrast media maps the territory of the coronary artery: an MRI technique for assessing the effects of locally delivered angiogenic therapies

RATIONALE AND OBJECTIVES

The effects of locally delivered angiogenic factors or stem cells on the coronary artery perfusion territory are not well defined. Therefore, the aim of this study was to determine the ability of the selective injection of magnetic resonance contrast media (MR-CM) to map and quantify the territories of the major coronary arteries.

MATERIALS AND METHODS

Selective coronary catheterization (n = 16 pigs) was performed under x-ray and magnetic resonance imaging (MRI) fluoroscopy in an x-ray and magnetic resonance suite. Catheters were placed in the left anterior descending (LAD), circumflex, or right coronary artery. The coronary perfusion territories were mapped by the intracoronary injection of MR-CM using first-pass perfusion (FPP) and early contrast-enhanced (CE) MRI. Cine MRI was used to quantify left ventricular (LV) mass. In 12 animals, the LAD coronary artery was occluded by microspheres to create infarctions. Infarct size was measured on delayed enhanced (DE) MRI after the intravenous injection of MR-CM.

RESULTS

X-ray and magnetic resonance fluoroscopy were successfully used to catheterize the coronary arteries. The perfusion territories of the coronary arteries were defined as hyperenhanced regions on FPP and CE MRI. The LAD coronary artery territory was 33.7 +/- 2.2% of LV mass on FPP MRI and 33.0 +/- 2.3% on CE MRI (P = .63). Bland-Altman analysis showed close agreement between the two methods (0.7 +/- 5.0%). DE MRI demonstrated the infarcted myocardium as hyperenhanced subregions of the perfusion territory (7.5 +/- 1.2% of LV mass).

CONCLUSIONS

Interventional cardiac x-ray and magnetic resonance fluoroscopy can be used to map and quantify the perfusion territory of each coronary artery. This experimental method can be used before and after the local delivery of angiogenic factors and stem cell therapy to determine their efficacy.

Can MR imaging be used to determine the efficacy of gene therapy in the heart?

In this issue of Radiology, Saeed et al (1) describe the intramyocardial administration of VM202, a newly constructed plasmid human hepatocyte growth factor, in a pig model of myocardial infarction. Histopathologic findings were used to characterize and quantify neovascularization, while magnetic resonance (MR) imaging findings were used to quantify left ventricular function, perfusion, and infarct size. Compared with control animals, VM202-treated animals demonstrated an increase in number of capillaries, improved perfusion and left ventricular ejection fraction, and reduced infarct size.